1. Field of the Invention
This invention concerns an improved thermocouple for measuring the temperature of a flat strip moving through a heat treating furnace at high speeds, which thermocouple remains in contact with the moving strip.
2. State of the Art
In the manufacture of flat steel strip, it is sometimes necessary to heat treat the strip by processing coils of the strip through a closed, controlled atmosphere furnace. The strip, being in coil form and therefore of great length, must be moved through the furnace at high speed, in the range of 200-650 feet per minute. In some portions of the furnace, the strip moves horizontally, and in other portions of the furnace, it moves vertically, all as is well known in the art. There is a plurality of different temperature zones in the furnace which must be individually controlled in order to control the temperature of the strip therein, so as to achieve the desired strip properties.
It is critical to be able to continuously measure the temperature of the strip in each temperature zone, for proper control of the process. Usually, such strip temperature measurement is done with appropriate infrared radiation pyrometers.
However, before such pyrometers can be effectively used, they must first have their emissivity settings adjusted. Such adjustment, using a thermocouple device to contact the surface of the moving strip, remain in contact therewith, and read out the actual temperature of the strip has not been accomplished successfully and accurately before the introduction of this invention.
As the strip moves through the furnace at high speeds, it may vibrate, either gently or in a somewhat rapid, irregular and forceful manner, due to mechanical shocks imparted by the machinery. Such vibration and shocks tend to cause prior art contact thermocouples to periodically lose contact with the strip surface, thus imparting inaccuracies into the temperature readings.
In addition, the frictional heat caused by the moving strip acting against the contact thermocouple may cause the thermocouple to indicate a higher temperature than is actually present, causing improper properties in the strip, due to inaccurate temperature settings in the furnace.
There is a need, therefore, for a contact thermocouple device for measuring strip surface temperature, which device can absorb the vibrations and shocks imparted to the strip, without losing contact with the moving strip surface, without marking or scratching the surface of the moving strip, and without temperature inaccuracies caused by frictional heat.
There is a further need for such a thermocouple device which can be used for strip moving generally horizontally through a furnace portion or also generally vertically through a furnace portion.